1. Field of the Invention
The present invention relates to a solid-state image sensing apparatus which has, e.g., an effective signal photoelectric conversion unit and a light-shielded reference signal photoelectric conversion unit to output a black level equivalent signal, and corrects the signal output level of the effective signal photoelectric conversion unit on the basis of the output signal from the reference signal photoelectric conversion unit.
2. Description of the Related Art
Conventionally, in image sensing using a solid-state image sensing apparatus, the pixel output variation at the time of reset must be corrected. To do this, correlated double sampling (CDS) is executed. In addition, to make the black level of a video signal constant, an error signal (dark current component) generated by a dark current must be subtracted from the video signal. To detect the dark current component, the output signal from a light-shielded pixel (optical black [OB] signal) is referred to.
However, in sensing a scene having extremely high luminance as a whole or a scene containing a high-luminance light source such as a spotlight, the OB signal level may vary. If black level correction is done by using the varying OB signal, the video signal may be inappropriate. There is a conventional technique-related to an image sensing apparatus (Jpn. Pat. Appln. KOKAI Publication No. 2002-290841). In this prior art, OB regions are prepared at a plurality of points near the effective pixel region including light-receiving elements which are arrayed on the light-receiving surface and generate pixel signals. Pixel signals are read out from both regions, thereby preventing any partial decrease in level of the pixel signals after black level correction.
Patent reference 1 above discloses several techniques for coping with the above-described situation, though none of them can solve the problem practically.